This invention is generally directed to processes for affecting the preparation of particles, and more specifically the present invention is directed to the preparation of colored toner compositions by dispersion polymerization. In one embodiment, thus the present invention encompasses dispersion polymerization processes wherein a monomer with a dye permanently attached thereto is selected. Accordingly, there can be prepared in a simple and economical manner self-colored particles inclusive of toner particles by the dispersion polymerization of two or more monomers, one of which is comprised of a dye molecule covalently attached to a monomer component. Depending on the processing parameters, particle sizes of, for example, from about 5 to 20 microns are achievable; however, particles with a smaller size of from, for example, about 0.1 to 3 microns can also be generated. Therefore, the resulting particles are useful as dry toner particles, or liquid toner compositions. These toner compositions can be selected for enabling the development of images in electrostatographic imaging, particularly electrostatic imaging systems, inclusive of dry and liquid development processes.
The development of images, and in particular electrostatic images utilizing developer compositions with toner materials, is well known. In many of these processes, an electrostatic latent image is formed on a photoconductive member, followed by development with a dry toner composition comprised of resin component and carbon black. Subsequently, the developed image is transferred to a suitable substrate wherein fixing is accomplished by, for example, heat. There is also known development systems wherein the images are rendered visible with liquid developer compositions.
Emulsion or suspension polymerization processes for obtaining toner compositions are also known. There is thus disclosed in U.S. Pat. No. 4,282,304 a suspension polymerization method wherein magnetic particles are first mixed with monomer and an initiator. Subsequently this mixture is suspended in an aqueous medium wherein a reaction within each particle ensues. The particles formed are then removed from the aqueous medium, and further processed for use as toner compositions. Also, there is disclosed in the prior art the selection of stabilizing compounds inclusive of methylhydroxy propyl cellulose for obtaining toner compositions prepared by emulsion or suspension polymerizations.
Furthermore, in U.S. Pat. No. 4,524,199, the disclosure of which is totally incorporated herein by reference, there is described a stable polar dispersion with nonionic amphiphathic steric stabilizers irreversibly anchored to a polymer particle. Stabilizers disclosed in this patent are cellulose compounds including hydroxyethyl cellulose. Also, in U.S. Pat. No. 4,476,210, the disclosure of which is totally incorporated herein by reference, there is described a stable colored liquid developer comprised of an insulating liquid dispersion medium having dispersed therein marking particles comprising a thermoplastic resin core substantially insoluble therein. There is further included in the aforementioned liquid developer an amphipathic block, or graft copolymeric soluble steric stabilizer irreversibly, chemically or physically attached to the thermoplastic resin core. Furthermore, there is included in the liquid developer of the U.S. Pat. No. 4,476,210 patent a colored dye imbibed in the thermoplastic resin core, the dye being soluble in the core, and insoluble in the dispersion medium. Examples of dyes that may be selected include Orasol Blue GN, Orasol Red 2BL, Orasol Blue BLN, Orasol Yellow, Morfast Red 101, Savinyl Pink CDLS, and Savinyl Red 3BLS. The process of the present invention is similar to the dispersion polymerization process of the aforementioned patent with the exception that in the present process there is selected a further monomer with a dye permanently attached thereto enabling the preparation of colored particles in a direct manner.
Also, with the process of the present invention, there can be provided the direct coloring of the particles thereby eliminating the need for separate processing steps. Further, the process of the present invention prevents the diffusion of the dye moles from inside of the particles thereby permitting the electrical characteristics of the marking materials to be retained during storage. Additionally, the covalent attachment of the colorant into the polymer backbone in accordance with the process of the present invention assists in eliminating and/or reducing the harmful toxicological effects of the colorant. Furthermore, the process of the present invention does not require a separate dyeing step as is the situation with the process illustrated in U.S. Pat. No. 4,476,210.
There is also described in Canon Japanese Patent Publication No. 5964853 toners for electrophotography obtained by copolymerizing colored monomers obtained from the reaction of nigrosine or other organic dyes with halogen containing monomers. According to the abstract of this publication, the resulting toner has ample coloration and does not produce background fog. In contrast to the process of the present application, the toner of the Canon patent publication is prepared by suspension polymerization. In this suspension polymerization process, the monomer/dye mixture is initially suspended in an aqueous medium to enable the formation of an emulsion. With dispersion polymerization processes, the monomers and amphiphatic stabilizers selected are initially soluble in an aqueous or nonaqueous dispersion medium. As the dispersion polymerization proceeds, particles are formed to yield a two phase system. An advantage of the dispersion polymerization process resides in its ability to control both the particle size and the particle size distribution of the final polymer particles relative to other particle polymerization processes such as suspension polymerization. Further, dispersion polymerization processes usually generate largely electrostatically neutral particles since the number of constituents present therein is substantially less, and also these constituents are all nonionic species.
There thus continues to be a need for improved processes for preparing colored toner particles useful as dry toner compositions, or liquid toner compositions. More specifically, there remains a need for generating self-colored toner particles by a simple and economical process. Additionally, there is a need for dispersion polymerization processes wherein toner particles of an appropriate size diameter can be generated in a single processing step. Also, there is a need for processes that permit colored toner compositions by dispersion polymerization wherein there is selected a monomer component having attached thereto a dye moiety. There also remains a need for dispersion polymerization processes wherein there is selected as one of the monomers a chromophore covalently linked to a polymerizable group inclusive of vinyl, methacryloyl or acryloyl moieties. Furthermore, there is a need for dispersion polymerization processes where there can be generated toner particles of a diameter of from about 0.1 to about 20 microns. There is also a need for obtaining dry, or liquid toner compositions which are useful for affecting the development of images in electrographic imaging processes inclusive of xerographic processes.